We have demonstrated that estimates of the functional impact of headaches and their impact on health-related quality of life (HRQOL) can be substantially improved using item response theory (IRT) and competing objectives of more practical and more precise assessments can be achieved over a wide range of severity levels using computerized adaptive testing (CAT), which matches items to each patient's level. If more available, such information could be useful in enhancing patient-caregiver communication. Among the limiting factors is the impracticality (respondent burden) of today's HRQOL measures. Short-forms (e.g., SF-36 (r), MIDAS) are more practical, however, "ceiling" and "floor" effects limit their ranges and they lack the precision to detect changes in individual patient scores. To address these deficiencies, the aims of Phase I are to use previously-developed IRT calibrations for a combined "pool" of items from headache-specific questionnaires covering major domains of headache impact to: (1) combine headache impact assessments with generic HRQOL assessments and display their results in tandem in a single user-friendly patient report; (2) obtain preliminary estimates of item usage, respondent burden (number of items required and administration times), range of levels measured (ceiling and floor effects), and score accuracy in comparison with a full-length survey; (3) comparison of the measurement precision of DYNHA(r)-HIT TM scores using the new enhanced item pool in comparison with items from the original item pools1; (4)evaluation of the acceptance of CAT administrations relative to full-length questionnaires; and (5) evaluation of the patient's experience using the prototype feedback report. The product of Phase I will be a prototype comprehensive HEADACHE-CAT with preliminary evidence regarding feasibility, acceptability and empirical performance. In Phase II, we will "marry" the new headache -specific CAT with item pools for generic CAT forms (based on SF-36 and other widely-used HRQOL measures) to create a single comprehensive system. A substantial advantage of our approach is the ability to utilize IRT models to cross-calibrate the new metrics with scores from current widely used headache-specific and generic impact tools to enable meaningful comparisons of results. HEADACHE-CAT software, programmed to be fully operational on the Internet and PC-compatible, will facilitate clinical research and improve assessment methods for use in clinical practice. Output will be evaluated in terms of reliability, validity and precision of scores. By greatly lowering data collection costs, reducing respondent burden, eliminating "ceiling" and "floor" effects and increasing the precision of individual patient scores, routine monitoring of HRQOL may become feasible as a clinical tool among headache sufferers and patients with other chronic illnesses. [unreadable] [unreadable]